1. Field of the Invention
The present invention deals with heat shields for use in connection with hot pipes and, in particular, for use with coke oven ascension pipes.
2. Description of the Prior Art
The need to protect workmen from injury due to contact with hot pipes and discomfort from radiant heat eminating from such pipes is one that is common to a number of industries. Conventionally, such protection is provided by wrapping insulating material around the pipe or by completely or partially enclosing the pipe within a spaced peripheral shield so as to create an insulating air space adjacent the pipe. It is found, however, that in certain cases, any such method which has the effect of decreasing heat flow from the pipe, itself, may also have the effect of increasing the pipe's internal temperature to an unacceptable level. Furthermore, in certain situations, a vertical pipe may be positioned so that one of its sides faces a work area while its other side is adjacent a wall or is otherwise facing some area not frequented by workmen. In such cases, it may be desirable to provide relatively more protection on the side of the pipe facing the work space than on the side with which workmen are not likely to come into contact. The advantage of being able to position an area of maximum protection at a particular circumferential section of the pipe might not, however, be readily attainable when a uniform insulating layer is used on a pipe.
In the case of coke ovens, for example, a number of workmen are usually assigned to various duties on the battery top. Along the sides of the battery top, coke oven ascension pipes project upwardly to connect ducts in the roof with a collecting main that runs alongside the coke oven. The surface temperatures of these ascension pipes may reach 700.degree. F., and in order to protect workers on the battery top from being accidentally burned by contact with these ascension pipes, as well as to decrease the radiant heat from the pipes to which these workers are exposed, it is important that an effective heat shield be provided on the side of the ascension pipe which faces inwardly toward the center of the battery top. The efficiency, on the other hand, of any heat shield on the side which faces outwardly over the side of the coke oven, is probably of less concern since workmen are probably less likely to directly touch or be exposed to radiant heat from that side of the ascension pipe.
Heat shields heretofore in use on coke oven ascension pipes have, in general, consisted of a single sheet of metal which is remotely connected to the ascension pipe, usually only on its side which faces inwardly toward the oven roof, so as to form an air space between the shield and the ascension pipe. A heat shield of this type is shown, for example, at numeral 14 in the drawings of U.S. Pat. No. 4,197,164. While such heat shields are known to provide some protection, it is found that at times they may reach temperatures which might be considered hazardous to nearby workmen. In view of these difficulities associated with ascension pipe heat shields heretofore in use, it has been suggested that ascension pipes be wrapped with a layer of external insulation so as to still further lower their external temperature. It is, however, believed that such a layer of insulation would retain heat to an extent so as to cause the internal temperature of the ascension pipes to rise to a point which might be detrimental to the pipe. It is, therefore, the object of the present invention to provide a heat shield which maximizes protection on the inner side of the ascension pipes and which, at the same time, dissipates heat so as to prevent pipe damage.